In many mono-audio systems a single sound source is outputted through a number of speakers or one speaker, regardless of the number of speakers. In a stereo-audio system a stereoscopic sound effect is implemented by outputting audio signals from different sound sources to two speakers.
Also, in a surround system the sound composed by two or more sound sources is reproduced, and outputted to a number of speakers. For example, currently, the most widely used 5.1-channel surround system outputs five different sound sources, and the source which emphasizes the bass portion of the five different sound sources is outputted through a sixth speaker.
Currently, the surround sound is implemented by using a number of wireless communication terminal, but there is the problem with this implementation of the surround sound system that limits its use to non-calling times (e.g., cannot be used when calling), due to the characteristics of the wireless communication terminals.